Methods for forming chalcogenide glass-based memory elements

Abstract

The present invention provides a design for a PCRAM element which incorporates multiple metal-containing germanium-selenide glass layers of diverse stoichiometries. The present invention also provides a method of fabricating the disclosed PCRAM structure.

1. A method of fabricating a memory element comprising the acts of:
 forming a first chalcogenide glass layer, said first chalcogenide glass layer having a first stoichiometry;  
 introducing a metal into said first chalcogenide glass layer to form a first metal-containing chalcogenide glass layer;  
 forming a second chalcogenide glass layer, said second chalcogenide glass layer having a second stoichiometry different from said first stoichiometry; and  
 introducing a metal into said second chalcogenide glass layer to form a second metal-containing chalcogenide glass layer.  
 
     
     
       2. A method of  claim 1  wherein said first chalcogenide glass layer comprises a first germanium-selenide glass layer and said second chalcogenide glass layer comprises a second germanium-selenide glass layer. 
     
     
       3. A method of  claim 2  wherein said first and said second germanium-selenide glass layers have a stoichiometric composition of about Ge x Se 100−x . 
     
     
       4. A method of  claim 3  wherein the value of x for said first germanium-selenide glass layer is greater than the value of x for said second germanium-selenide glass layer. 
     
     
       5. A method of  claim 4  wherein the value of x for said first germanium-selenide glass layer is about 38 to about 43 and the value of x for said second germanium-selenide glass layer is about 18 to about 33. 
     
     
       6. A method of  claim 5  wherein the value of x for said first germanium-selenide glass layer is about 40 and the value of x for said second germanium-selenide glass layer is about 25. 
     
     
       7. A method of  claim 3  wherein the value of x for said first germanium-selenide glass layer is less than the value of x for said second germanium-selenide glass layer. 
     
     
       8. A method of  claim 3  wherein silver is introduced into said first and said second germanium-selenide glass layers. 
     
     
       9. A method of  claim 8  wherein the step of introducing silver into any of the said first or said second germanium-selenide glass layers having a value of x between about 18 and about 33 comprises the steps of:
 depositing a silver-containing layer over said any of the said first or said second germanium-selenide glass layers having a value of x between about 18 and about 33;  
 irradiating said any of the said first or said second germanium-selenide glass layers having a value of x between 18 and about 33 with electromagnetic radiation of wavelength of about 200 nm to about 600 nm for approximately 5 to about 30 minutes at from about 1 mW/cm 2  to about 10 mW/cm 2 .  
 
     
     
       10. A method of  claim 9  further comprising removing residual silver-containing layer from over irradiated said any of the said first or said second germanium-selenide glass layers having a value of x between 18 and about 33. 
     
     
       11. A method of  claim 9  further comprising thermally heating said silver containing layer and said first or said second germanium-selenide glass layer at a temperature of about 50° C. to about 350° C. for about 5 to about 15 minutes. 
     
     
       12. A method of  claim 11  comprising the step of thermally heating said silver containing layer and said first or said second germanium-selenide glass layer at a temperature of about 110° C. 
     
     
       13. A method of  claim 9  wherein said silver-containing layer comprises silver-selenide. 
     
     
       14. A method of  claim 8  wherein the step of introducing silver into any of said first of said second germanium-selenide glass layers having a value of x between about 38 and about 43 comprises the steps of:
 depositing a silver-containing layer over said any of said first or said second germanium-selenide glass layers having a value of x between about 38 and about 43;  
 allowing silver from said silver-containing layer to migrate into said any of said first or said second germanium-selenide glass layers having a value of x of about 38 to about 43.  
 
     
     
       15. A method of  claim 14  further comprising the step of removing residual silver-containing layer from over said first or said second germanium-selenide glass layer. 
     
     
       16. A method of  claim 14  wherein said silver-containing layer comprises silver-selenide. 
     
     
       17. A method of  claim 1  further comprising the act of forming a first electrode coupled to said first metal-containing chalcogenide glass layer. 
     
     
       18. The method of  claim 17  wherein said first electrode comprises tungsten. 
     
     
       19. The method of  claim 1  further comprising the act of forming a second electrode coupled to said second metal-containing chalcogenide glass layer. 
     
     
       20. The method of  claim 19  wherein said second electrode comprises silver. 
     
     
       21. A method of fabricating a memory element comprising the steps of:
 forming a first chalcogenide glass layer, said first chalcogenide glass layer having a first glass matrix structure;  
 introducing metal into said first chalcogenide glass layer to form a first metal-containing chalcogenide glass layer;  
 forming a second chalcogenide glass layer, said second chalcogenide glass layer having a second glass matrix structure diverse from said first glass matrix structure;  
 introducing metal into said second chalcogenide glass layer to form a second metal-containing chalcogenide glass layer;  
 forming at least one additional chalcogenide glass layer, said at least one additional chalcogenide glass layer having a glass matrix structure different from the glass matrix structure of any metal-containing chalcogenide glass layer adjacent to said at least one additional metal-containing chalcogenide glass layer; and  
 introducing metal into said at least one additional chalcogenide glass layer to form at least one additional metal-containing chalcogenide glass layer.  
 
     
     
       22. A method of  claim 21  wherein said first chalcogenide glass layer comprises a first germanium-selenide glass layer, said second chalcogenide glass layer comprises a second germanium-selenide glass layer, and said at least one additional chalcogenide glass layer comprises at least one additional germanium-selenide glass layer. 
     
     
       23. A method of  claim 22  wherein said first, said second, and said at least one additional germanium-selenide glass layers have a stoichiometric composition of about Ge x Se 100−x . 
     
     
       24. A method according to  claim 23  wherein the value of x for said at least one additional germanium-selenide glass layer equals the value of x of any other germanium-selenide glass layer, wherein said any other germanium-selenide glass layer is not positioned consecutively to said at least one additional germanium-selenide glass layer. 
     
     
       25. A method of  claim 24  wherein said at least one additional germanium-selenide glass layer comprises a third germanium-selenide glass layer. 
     
     
       26. A method of  claim 25  wherein the value of x for said first and said third germanium-selenide glass layers is equal. 
     
     
       27. A method of  claim 26  wherein the value of x for said first and said third germanium-selenide glass layers is greater than the value of x for said second germanium-selenide glass layer. 
     
     
       28. A method of  claim 27  wherein the value of x for said first and said third germanium-selenide glass layers is from about 38 to about 43 and the value of x for said second germanium-selenide glass layer is from about 18 to about 33. 
     
     
       29. A method of  claim 28  wherein the value of x for said first and said third germanium-selenide glass layers is about 40 and the value of x for said second germanium-selenide glass layer is about 25. 
     
     
       30. A method of  claim 23  wherein the value of x for said at least one additional germanium-selenide glass layer is diverse from the value of x for other silver-containing germanium-selenide glass layers. 
     
     
       31. A method of  claim 30  wherein the values of x for each of said first, said second, and said at least one additional germanium-selenide glass layer ascend from said first electrode to said second electrode. 
     
     
       32. A method of  claim 30  wherein the values of x for each of said first, said second, and said at least one additional germanium-selenide glass layer descend from said first electrode to said second electrode. 
     
     
       33. A method of  claim 23  wherein said metal comprises silver. 
     
     
       34. A method of  claim 33  wherein the step of introducing silver into any of the said first, said second, or said at least one additional germanium-selenide glass layers having a value of x between about 18 and about 33 comprises the steps of:
 depositing a silver-containing layer over said any of the said first, said second, or said at least one additional germanium-selenide glass layers having a value of x between about 18 and about 33;  
 irradiating said any of the said first, said second, or said at least one additional germanium-selenide glass layers having a value of x between about 18 and about 33 with electromagnetic radiation of wavelength of about 200 nm to about 600 nm for approximately 5 to about 30 minutes at from about 1 mW/cm 2  to about 10 mW/cm 2 .  
 
     
     
       35. A method of  claim 34  further comprising removing residual silver-containing layer from over irradiated said any of the said first, said second, or said at least one additional germanium-selenide glass layers having a value of x between about 18 and about 33. 
     
     
       36. A method of  claim 34  further comprising thermally heating said silver containing layer and said any of the said first, said second, or said at least one additional germanium-selenide glass layers having a value of x between about 18 and about 33 at a temperature of about 50° C. to about 350° C. for about 5 to about 15 minutes. 
     
     
       37. A method of  claim 36  comprising the step of thermally heating said silver containing layer and said any of said first, said second, or said at least one additional germanium-selenide glass layer having a value of x between about 18 and about 33 at a temperature of about 110° C. 
     
     
       38. A method of  claim 34  wherein said silver-containing layer comprises silver-selenide. 
     
     
       39. A method of  claim 33  wherein the step of introducing silver into any of the said first, said second, or said at least one additional germanium-selenide glass layers having a value of x between about 38 and about 43 comprises the steps of:
 depositing a silver-containing layer over said any of the said first, said second, or said at least one additional germanium-selenide glass layer having a value of x between about 38 and about 43;  
 allowing silver from said silver-containing layer to migrate into said any of said first, said second, or said at least one additional germanium-selenide glass layer having a value of x between about 38 and about 43.  
 
     
     
       40. A method of  claim 39  further comprising the step of removing residual silver-containing layer from over said any of said first, said second, or said at least one additional germanium-selenide glass layer having a value of x between about 38 and about 43. 
     
     
       41. A method of  claim 39  wherein said silver-containing layer comprises silver-selenide. 
     
     
       42. A method of  claim 21  further comprising the step of forming a first electrode coupled to said first metal-containing chalcogenide glass layer. 
     
     
       43. A method of  claim 42  wherein said first electrode comprises tungsten. 
     
     
       44. A method of  claim 21  further comprising the step of forming a second electrode coupled to the last formed said at least one additional metal-containing chalcogenide glass layer. 
     
     
       45. A method of  claim 44  wherein said second electrode comprises silver.